In a large mixing bowl, combine the all-purpose flour, salt, and instant yeast. Stir to mix evenly.
Add the warm water to the dry ingredients and mix with a wooden spoon or spatula until a shaggy, sticky dough forms. Ensure all flour is incorporated.
Cover the bowl tightly with plastic wrap or a clean kitchen towel and let it rest at room temperature for 12 to 18 hours, until the surface is dotted with bubbles and the dough has doubled in size.
Lightly flour a clean work surface and turn the dough out onto it. Using floured hands, gently fold the dough over itself once or twice to form a rough rectangle. Do not knead.
Divide the dough into four equal portions using a bench scraper or knife. Shape each portion into a rough baguette shape by folding the dough lengthwise and gently rolling it to elongate, tapering the ends slightly.
Place the shaped baguettes on a parchment-lined baking sheet dusted with cornmeal or flour. Cover loosely with a kitchen towel and let them rise for 1 to 2 hours, until puffy but not doubled.
About 30 minutes before baking, preheat your oven to 450°F (230°C). Place a baking stone or inverted baking sheet on the middle rack and a shallow pan on the bottom rack.
Just before baking, use a sharp knife or lame to make 3 to 4 diagonal slashes on each baguette about 1/4 inch deep.
Transfer the baguettes on the parchment to the preheated baking stone or inverted baking sheet. Pour 1 cup of hot water into the shallow pan on the bottom rack to create steam and quickly close the oven door.
Bake for 20 minutes, then rotate the baking sheet and bake for an additional 15 to 20 minutes, until the baguettes are deep golden brown and sound hollow when tapped on the bottom.
Remove the baguettes from the oven and transfer them to a wire rack to cool completely before slicing.